This invention relates to the hydroformylation of unsaturated hydrocarbons. In hydroformylation processes, carbon monoxide and hydrogen are reacted with an olefin to produce the corresponding hydroxymethyl-substituted or formyl-substituted derivative of the olefin. These processes are of great industrial importance in converting olefins, to aldehydes and alcohols. Other products such as esters, acids, and amides can generally be prepared in analogous processes by adding the carbonyl moiety or the hydroxymethyl moiety to one of the carbon atoms situated at a double bond of the olefin.
U.S. Pat. No. 5,488,174 describes a hydroformylation process which employs a catalyst system comprising a source of palladium and a bidentate ligand of the formula R.sub.1 R.sub.2 M.sub.1 RM.sub.2 R.sub.3 R.sub.4 in which M.sub.1 and M.sub.2 independently may be phosphorus, arsenic, or antimony atoms. R is a bivalent organic bridging group and R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are unsubstituted or substituted aliphatic groups. One or more combinations of R.sub.1, R.sub.2, R.sub.3, and R4 form a bivalent cyclic group. These ligands can include, for example, a 1,2-bis(phosphabicyclononyl)ethane.
Generally, when such a process is used in hydroformylation, a halide salt such as NaCl or NaI is used as promoter and a cosolvent such as sulfalone is added. The promoters generally improve the reaction rate, reduce paraffin make, and increase the linearity of products, relative to the same process without the addition of promoter. These processes have high selectivity and conversion.
U.S. Pat. No.5,436,356 describes a carbonylation process using a catalyst system of the type described above. The patent further describes the use of drying agents in such processes with trimethyl orthoformate being the preferred drying agent. Such drying agents react with water to form an alcohol (e.g., methanol) and an ester (e.g. methyl formate). This ensures that the desired ester is produced instead of the related acid. Thus, such an addition of trimethyl orthoformate is useful in carbonylation processes when the presence of water is to be minimized. Such agents would not find utility in processes deliberately conducted in the presence of water.
It is well known that halides such as chlorine can damage or destroy metal reactors. It is desirable to employ a hydroformylation process which achieves the same or similar performance as those described above without deleteriously affecting the reactors or vessels used.